Factors Controlling Climate Climate – average weather of a region

Factors Controlling Climate Daily & annual cycles Daily rotation of the Earth (day/night) Annual revolution around the sun (seasons) Longer-term cycles: El Nino – several years Continental Glaciation – hundreds of thousands of years Factors influencing annual cycle of air temp:

Factors Controlling Climate Factors influencing annual cycle of air temperature: Latitude Altitude Coastal vs. Continental location Factors influencing precipitation: The three above, plus: Annual & daily air temperaturess Prevailing air masses Relation to mountain barriers Position of persistent low & high pressure center Prevailing winds & ocean currents

Temperature Regimes Temp Regime – Annual cycle of temp driven by latitude & location Insolation is main control on temperature Variation in insolation due to latitude Effect of marine or continental location moderates variation

Precipitation Regimes Seven global precipitation regions: 1. Wet Equatorial Belt - >2000 mm (80 in) rainfall mE air masses – heavy convective rainfall 2. Trade-wind Coasts – 1500-2000 mm precip Narrow belts from Equator to 30° N & S on east coast of continents mT air masses carried on trade winds bring rainfall 3. Tropical Deserts - < 250 mm rainfall Located on or near tropics cT air masses under subtropical highs

Precipitation Regimes 4. Midlatitude deserts & steppes – 100-500 mm precip In centers of continents, 30-50°N In rainshadow of mountain chains to west 5. Moist Subtropical – 1000-1500 mm precip 25-40° N & S on moist, western side of subtropical high mT air masses from ocean provide moisture for precip

6. Midlatitude West Coast – 1500-2000+mm precip On west coasts of continents in path of moist westerlies mP air masses & orographic precipitation 7. Arctic & Polar Deserts - <300 mm precip Above 60°N & S cP & cA air masses can hold little moisture

Precipitation Regions Isohyets – lines drawn through areas with equal annual precipitation

Seasonality of Precipitation Timing of precipitation during year key to climate 3 types of precipitation patterns: Uniform throughout year Precipitation maximum during summer Precipitation maximum during winter

Climate Classification Based on mean monthly values of temp & precip 13 climate types based on: Air mass movements Frontal zones Climate types broken into 3 groups: Group I – low latitudes - cT, mE and mT air masses Group II – midlatitudes - Polar front, varied air masses Group III – high latitudes - cP, mP and cA air masses

Climograph Tool for defining the climate of a given location or region Mean monthly temp on line chart Mean monthly precip on bar chart May include dominant weather systems

Low-Latitude Climates (Group I) Wet Equatorial (1) – warm to hot w/abundant rainfall Example – Amazon Basin or Congo Trade Wind Coastal (2) – warm to hot w/very rainy season Example – any coastal region exposed to trade winds

Low-Latitude Climates (Group I) Wet-Dry Tropical (3) – warm to hot w/distinct wet & dry seasons Example – Sahel or monsoon region of central India Dry Tropical (4) – very hot in high-sun season, cooler in low sun Little to no rainfall Examples – Sahara Desert, Central Australia

Midlatitude Climates (Group II) Dry Subtropical (5) – not as hot as dry tropical Example – Death Valley, CA Moist Subtropical (6) – hot, humid summers, mild winters, ample rain Example – Southeastern US Mediterranean (7) – hot, dry summers, rainy winters Examples – Southern California, Mediterranean Sea

Midlatitude Climates (Group II) Marine West Coast (8) – warm summers, cool, wet winters Expls – Northwestern US Dry Midlatitude (9) – warm to hot in summer, cold winter, little precip Expl – Great Plains of North America Moist Continental (10) – warm summer, cold winter, ample precip. Expl – Northeastern US

High-Latitude Climates (Group III) Boreal Forest (11) – short, cool summers, long, very cold winters Example – Siberia, Central Alaska Tundra (12) – short, cool summers, winters slightly warmer than (11) Example – western Alaska coast Ice Sheet (13) – bitter cold all year Examples – inland Greenland and Antarctica